In some books a species called _Polypodium calcareum_ (The Limestone Polypody) is described. In some quarters this plant is regarded as a variety of _P. dryopteris_, as it is similar in some respects. Mr. C. T. Druery considers it to be a distinct species. The chief points of difference are said to be the following. The whole plant is larger in growth, whilst the green of the fronds is not such a golden colour, even in the early days. Also the pinnæ are not arranged so definitely in the form of three branches, as is to be observed in the case of the Oak Fern. Finally, the unrolling of the frond does not present the appearance of three little balls, seeing that each pinnæ unfolds separately. The Limestone Polypody occurs chiefly in the North of England. _Polypodium alpestre._ The Alpine Polypody. This is a most remarkable species, in that it bears a singular resemblance to the Lady Fern. By some authorities it is positively regarded as a Mountain form of the Lady Fern. The reason for linking the species with the Polypodies is found in the rounded sori, which have no indusia. The Alpine Polypody has a short tufted root-stock, and from this arise the fronds, which may be a foot or even more in height. The stipes is very short when compared with the leafy portion, and it is covered with brown scales. The general outline of the fronds is broadly lanceolate, and they are twice divided. The pinnæ are arranged in alternation on either side of the rachis, and these are divided into pinnules with blunt points. The pinnules have toothed edges. The sori are chiefly situated near to the inside border of the pinnules. Those who consider that the Alpine Polypody is a form of the Lady Fern call the species _Pseudathyrium alpestre_. The Alpine Polypody seems to be exclusively confined, as far as the United Kingdom is concerned, to the highlands of Scotland. It is sometimes to be found at an altitude of four thousand feet above sea-level. In spite of its restricted locality the Alpine Polypody is an easy subject for the garden, if it can be provided with a well-drained situation. CHAPTER IX THE ROYAL FERN Under the name of the Flowering Fern it is probable that most people are familiar with the subject we are now about to consider. The title has without a doubt arisen from the fact that the species bears its sori in masses at the termination of the fronds, quite apart from the leafy portion. The Royal Fern is the sole British representative of the family Osmundaceæ.